Power Steering Problems — What the Difference Between Hydraulic and Electric Systems Means for Diagnosis

Power steering faults present differently depending on whether the vehicle has a hydraulic system (driven by a pump connected to the engine) or an electric system (driven by a motor attached to the steering column or rack). Knowing which system the vehicle has is the first step, because the diagnostic approach, the common failure points, and the repair costs are entirely different.

Hydraulic power steering

Hydraulic power steering uses a pump driven by the engine via a belt to pressurise power steering fluid. The pressurised fluid is directed by a control valve in the steering rack to assist the steering effort. The system is simple, proven and relatively inexpensive to maintain, but it has mechanical wear points that deteriorate over time.

Common hydraulic power steering faults:

• Whining noise when turning — the most recognisable symptom of a failing power steering pump, particularly noticeable on full lock. Often accompanied by increased steering effort. Usually the pump itself, or low fluid level allowing air to be drawn in
• Fluid leak — from the pump, the high-pressure hose, the rack seal or the return line. Power steering fluid is thin and light amber; it typically collects near the front subframe and forward of the engine
• Heavy steering at low speed that lightens at higher speed — the system is still partially functioning. Indicates a pump delivering low pressure or a rack control valve that is worn
• Steering that is heavy on full lock only — often a pump that is adequate under normal conditions but cannot maintain pressure at extreme demand; sometimes a sign that the pump is close to failure

Electric power steering (EPS)

Electric power steering replaces the hydraulic pump with an electric motor that assists the steering rack or column directly. There is no fluid, no pump belt, and no connection to the engine. The system is controlled by an ECU that reads steering angle, vehicle speed and driver torque input and adjusts the assist level accordingly.

Common EPS faults:

• Power steering warning light with heavy steering — the EPS system has detected a fault and disabled the assist. The steering still works but requires full manual effort. Common causes include the EPS control module detecting an out-of-range torque sensor reading, a motor current fault, or an overtemperature event after prolonged low-speed manoeuvring
• Intermittent assist loss at low speed — often related to a torque sensor fault, a connector corrosion issue, or an EPS module that is producing marginal motor current. A full diagnostic scan with live data from the EPS module is required
• Steering that pulls to one side with no mechanical cause — can indicate an EPS motor providing asymmetric assist; sometimes confused with wheel alignment or tyre pressure issues. Shaw’s checks the obvious mechanical causes first before investigating the EPS
• Clunking or knocking through the steering wheel — can be a worn steering rack, a loose motor mounting on a column-assist EPS, or a universal joint in the steering column. The EPS motor itself rarely makes mechanical noise

Diagnosis at Shaw’s

Hydraulic power steering faults are generally identifiable through inspection, pressure testing, and road test. EPS faults require reading the EPS module fault codes and live data alongside the physical inspection. Shaw’s carries out both at our Kinmel Bay and Rhyl branches. Where a fault requires specialist EPS programming — such as a replacement rack that needs angle sensor initialisation — we advise on this as part of the repair estimate before any work begins.

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Shaw’s Service Station | Kinmel Bay & Rhyl | 01745 353481